Biology subjects

de Mendoza, D.

Publications and source records attributed to de Mendoza, D..

5 recordsLinked to original sources

bioRxiv2026

STARD3 mediates non-vesicular cholesterol transport in Caenorhabditis elegans

Cholesterol transport plays a pivotal role in regulating development and metabolism in Caenorhabditis elegans, a sterol-auxotrophic organism. Here, we identify the nematode cholesterol-binding protein STARD3 and provide structural and functional evidence for its role in non-vesicular sterol mobilization. Using biophysical and high-resolution structural methods, we show that the START domain (Ce-START) of C. elegans STARD3 binds cholesterol with high affinity and adopts a fold conserved with its human ortholog. Crystal structures of Ce-START in both apo and cholesterol-bound forms reveal key determinants of sterol recognition and conformational changes upon ligand binding. Functional analysis of a C. elegans stard3 knockout strain demonstrates that STARD3 is essential for cholesterol trafficking under sterol-limited conditions and that it genetically interacts with the NPC1/NPC2 pathway to sustain cholesterol mobilization. Collectively, these results establish STARD3 as a crucial cholesterol transporter in C. elegans and underscore the evolutionary conservation of START-domain proteins, reinforcing the utility of C. elegans as a model for studying intracellular cholesterol dynamics.

biophysics↗

bioRxiv2025

Unsaturated Fatty Acids Are Required for Germline Proliferation and Membrane Structural Integrity in Caenorhabditis elegans

Unsaturated fatty acids (UFAs) are critical components of membrane lipids, but their specific roles in germline development and reproductive health remain poorly defined. Here, we investigated the consequences of UFA depletion in the Caenorhabditis elegans germline using an auxin-inducible degron (AID) system to conditionally degrade FAT-7, the major {Delta}9 stearoyl-CoA desaturase, in a fat-5; fat-6 double mutant background. This strategy bypassed the lethality associated with complete loss of {Delta}9 desaturase activity, enabling analysis of UFA deficiency in adult animals. UFA depletion led to a dramatic reduction in brood size, elevated embryonic and larval lethality, and a severe loss of germline nuclei. We found that UFAs are essential for mitotic proliferation, DNA replication, and chromosome organization in the germline. Moreover, reduced UFA levels impaired meiotic progression, accompanied by loss of membrane integrity in the syncytial germline. Notably, UFA deficiency increased nuclear pore complex (NPC) signal intensity, suggesting alterations to the nuclear envelope (NE). Together, our findings demonstrate that UFAs are indispensable for germline maintenance, affecting cell cycle progression, chromosome organization, and membrane architecture. These results underscore a fundamental link between acyl chain composition and reproductive success, highlighting the critical role of lipid homeostasis in the germline. SummaryUnsaturated fatty acids (UFAs) are essential for fertility, but their role in germline maintenance remains unclear. In this study, we used Caenorhabditis elegans to examine how UFA depletion affects the germline. By conditionally disrupting UFA synthesis, we found that low UFA levels impair germline mitotic proliferation, DNA replication, meiotic progression, and germline membrane structures. These findings demonstrate that lipid composition is critical for germline maintenance and highlight a broader role for fatty acids in reproductive health, offering insights relevant to metabolic and fertility disorders in humans.

genetics↗

bioRxiv2024

An inducible and reversible system to regulate unsaturated fatty acid biosynthesis in C. elegans

Unsaturated fatty acids (UFAs) play crucial roles in various physiological and pathological processes. In animals, these lipids are synthesized from saturated fatty acids through the action of delta 9 ({Delta}9) desaturases. In C. elegans, three {Delta}9 desaturases are encoded by the genes fat-5, fat-6, and fat-7. The presence of multiple {Delta}9 desaturases has posed a significant challenge in developing a rapid and efficient approach to control UFA production in C. elegans and other model organisms. Utilizing the auxin-inducible degradation system, we specifically targeted the C. elegans fat-7 gene, responsible for the major stearoyl-CoA desaturase (SCD), while deleting fat-5 and fat-6. This design resulted in a strain that can be reversibly depleted of UFAs in the cells of interest. Conditional depletion in all somatic cells exhibited a pronounced auxin-dependent defect in UFA production. Using this system, we uncovered an essential requirement for de novo UFA production during L1 and L2 stage. Moreover, our results support a direct connection between UFA levels, fat storage and increased lipid turnover. This system will enable further studies exploring the cellular and physiological consequences of impairing UFA biosynthesis at different developmental stages or in specific tissues. SummaryUnsaturated fatty acids (UFAs) are essential for life. In animals, UFAs are synthesized by {Delta}9 desaturase enzymes. Caenorhabditis elegans possesses three {Delta}9 desaturase genes: fat-5, fat-6, and fat-7. We engineered a strain where fat-7 can be reversibly switched off while fat-5 and fat-6 are deleted, allowing precise control of UFA levels throughout the life cycle. Our findings demonstrate the critical role of UFA biosynthesis in early development and its direct link to fat storage and lipid turnover. This strain enables the study of UFA-related physiological and pathological processes in animals.

genetics↗

bioRxiv2023

Impaired cholesterol transport from aged astrocytes to neurons can be rescued by cannabinoids.

Cholesterol is crucial for the proper functioning of eukaryotic cells, especially neurons, which rely on cholesterol to maintain their complex structure and facilitate synaptic transmission. However, brain cells are isolated from peripheral cholesterol by the blood-brain barrier and mature neurons primarily uptake the cholesterol synthesized by astrocytes for proper function. This study aimed to investigate the effect of aging on cholesterol trafficking in astrocytes and its delivery to neurons. Using in vitro and in vivo models of aging, we found that aged astrocytes accumulated high levels of cholesterol in the lysosomal compartment, and this cholesterol buildup can be attributed to the simultaneous occurrence of two events: decreased levels of the ABCA1 transporter which impairs ApoE-cholesterol export from astrocytes, and reduced expression of NPC1, which hinders cholesterol release from lysosomes. We show that these two events are accompanied by increased microR33 in aged astrocytes, which is known to downregulate ABCA1 and NPC1. In addition, we demonstrate that the microR33 increase is triggered by oxidative stress, one of the hallmarks of aging. By co-culture experiments we also show that aging in vitro impairs the cholesterol delivery from astrocytes to neurons. Remarkably, we found that this altered transport of cholesterol could be alleviated through treatment with endocannabinoids as well as cannabidiol or CBD. Given that reduced neuronal cholesterol affects synaptic plasticity, the ability of cannabinoids to restore cholesterol transport from aged astrocytes to neurons holds significant implications in the field of aging.

neuroscience↗

bioRxiv2021

Unsaturated fatty acids profiling in live C. elegans using real-time NMR spectroscopy

Unsaturated fatty acids (UFAs) impact central cellular process in animals such as membrane function, development and disease. Perturbations of UFAs homeostasis contribute to the onset of metabolic, cardiovascular and neurodegenerative disorders. Nevertheless, links between lipid desaturation fluctuations and the dynamics of mono and polyunsaturated fatty acid synthesis in live animal physiology are poorly understood. To advance in the understanding of this process, we decided to study de novo UFAs synthesis with the highest resolution possible in live Caenorhabditis elegans. Conventional lipid analysis in this organism involves solvent extraction procedures coupled with analytical techniques such as chromatography and/or mass spectrometry. These methodologies are destructive and prevent the access of information, linking in vivo UFA dynamics and functionality. To overcome these limitations, we used uniform 13C isotope labeling and real-time 2D heteronuclear NMR spectroscopy in live C. elegans to identify their UFA compositions and the dynamic response of these fatty acids during cold adaptation. Our methodology allowed us to monitor in real time the upregulation of UFA synthesis when ambient temperature is decreased. The analysis of UFAs synthesis in worms lacking the adiponectin receptor AdipoR2 homolog PAQR-2 during a temperature drop supports the pivotal role of this protein in low temperature adaptation and survival. Our results provide new insights about the environmental regulation of UFAs and establish methodological benchmarks for future investigations of fatty acid regulation under experimental conditions that recapitulate human diseases.

biophysics↗